A case of multiosseous osteosarcoma in a 15-year-old girl is presented. Neoplastic foci were initially diagnosed in the right ilium and left mandible. The clinical course was complicated by pregnancy and chemotherapeutic side effects. Postmortem examination revealed multiple tumor emboli in the lungs. The literature concerning metastatic and multicentric origins of multiosseous osteosarcomas is reviewed. The case presented probably represents mandibular metastasis from the ilium.